<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>对象学习</title>
    <script src="test.js"></script>
    <link rel="stylesheet" href="mystyle.css"/>
</head>
<body>
<button type="button" onclick="case1()">case1</button>
<br><br>

<button type="button" onclick="case2()">case2</button>
<br><br>

<button type="button" onclick="case3()">判断对象中是否存在某个元素</button>
<br><br>
</body>
</html>